The present invention relates to a flat-panel display device used in, e.g., a car navigation apparatus.
A Hi-Vision television receiver and a car navigation apparatus which has prevailed recently contain a flat display screen having an aspect ratio 9:16. Particularly, the car navigation apparatus is designed to drive the flat display panel such as a liquid crystal display panel using a DC power supply of 12 V supplied from a battery. As the density of the pixel electrodes for driving liquid crystals is increased to obtain an display image of a higher resolution, the insulating property of the panel becomes insufficient. Hence, the apparatus must have a display driving circuit designed such that the liquid crystal display panel is driven with a voltage as low as possible.
However, the video signal must have a relatively large voltage amplitude between black and white levels to obtain a satisfactory contrast value in an image displayed on the flat display panel. In addition, this video signal also requires a voltage amplitude for a horizontal synchronization signal incorporated therein. Hence, it is difficult in design to reduce the withstand voltage of the display driving circuit.
It is an object of the present invention to provide a flat-panel display device whose arrangement enables reduction in the withstand voltage of a display driving circuit.
A flat-panel display device according to the present invention comprises a flat display panel; a video signal input unit for receiving an analog video signal which is set at a reference level in a horizontal blanking period and varies within a range from the reference level to a maximum level in a horizontal effective image period; and a display driving circuit for driving the flat display panel on the basis of the analog video signal from the video signal input unit; wherein the display driving circuit includes a level conversion unit for converting the reference level of the analog video signal into an intermediate level determined between the reference and maximum levels in the horizontal blanking period.
With the flat-panel display device, the level conversion unit converts the reference level of the analog video signal into an intermediate level determined between the reference and maximum levels corresponding to black and white levels in the horizontal blanking period. Therefore, the maximum amplitude of the analog video signal can be reduced in a case where a horizontal synchronization signal is incorporated in the analog video signal. Since the ratio of the voltage amplitude of the horizontal synchronization signal to that of the analog video signal can be decreased, the withstand voltage of the display driving circuit can be lowered without changing the contrast value determined by the black and white levels.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.